The present invention relates to the field of gear arrangements, and in particular to gear arrangements constructed of dissimilar materials.
Gear arrangements are known for example from German patent DE1961982. The gear combination disclosed in this German patent provides gears that rotate on a common shaft, and the teeth of one gear are arranged side by side relative to the teeth of another gear. The larger gear is made of plastic and the smaller gear is made of metal. Both gears are arranged stationarily and fixedly relative to one another on the shaft, for example with a key and keyway. Similar gear arrangements are disclosed in German patents DE2602152A1, DE3026685A1, DE846192C and U.S. Pat. No. 3,719,103. In the above-cited gear combinations the gears made of different construction materials are, in contrast, rigidly fixed on the shaft or fixed, for example cemented to one another, with their surfaces facing toward one another. In this way slipping of the gears relative to one another in the direction of rotation is impossible.
In transmissions, gears engaging with one another transmit force and torque. However, the engagement of the teeth of the gears with one another causes disturbing and sometimes rather loud and unpleasant noise. For noise damping, the gears can be made of suitable materials such as plastic. Further noise reduction can be achieved by helical toothing of the gears.
While gears made of plastic are distinguished by the advantage of less noise, they have the disadvantage of lower strength. Similarly, gears made of metal display high strength but produce relatively loud noise. For transmission gears, one therefore seeks to find a material that produces low noise but has the requisite strength requirements. Therefore, there is often a design compromise between higher strength versus less noise.
Therefore, there is a need for improved gear arrangements.